The central organization of the vagus nerve innervating the colon of the rat

The extent to which the vagus nerve innervates the colon remains controversial.In 29 rats the tracer cholera toxin-horseradish peroxidase was injected into the cecum, the ascending, transverse, or descending colon or the rectum. For comparison, control injections were made into the stomach.For all areas of colon except the rectum, brainstem motoneuronal labeling was limited to the lateral third of the dorsal motor nucleus of the vagus nerve bilaterally. In contrast, gastric injections resulted in motoneuronal labeling limited to the medial portions of the nucleus. The number of labeled motoneurons was greatest following injection of the cecum, and it significantly decreased for the more distal areas of the colon. Colonic motoneuron dendrites projected into the nucleus of the solitary tract and within the dorsal motor nucleus of the vagus nerve. Sensory afferent terminal labeling was limited to the commissural and medial subnuclei of the nucleus of the solitary tract. For the rectum, sensory and motor labeling was limited to the spinal cord.The distribution of labeling within the vagal complex indicates that all regions of the colon, except the rectum, are innervated by the celiac and accessory celiac branches of the vagus nerve.